From the author of

Microsoft's Software Licensing

The key reasons for choosing an alternative to Windows lie with the Microsoft
software licensing, which is blossoming into an expensive nightmare for many
large and small organizations. This licensing causes these organizations to
perform a cost analysis for using Microsoft software versus using something else
that is equally effective and much cheaper to license and manage licenses. For
example, every Windows PC must have a software license for Windows running on
that PC and another license if that PC accesses a Windows server. Additional
licenses are needed for using special Windows software such as Microsoft Office,
and special server software requires additional licenses. Each license means
extra revenue for Microsoft. Even with corporate bulk-licensing agreements, it
is still a nightmare to track the licenses on all enterprise PCs. Windows and
other software vendors provide special software to automate the process. Even
so, this still requires constant costly monitoring.

Microsoft would justifiably argue that these license fees are perfectly
legal, and that they are necessary to continue development of new and more
productive Windows products. (This may or may not be true.) Does everyone in an
organization need the latest and "best" Microsoft software? Is the
latest Microsoft software the best Microsoft software? I did not see any Windows
Me users standing up in agreement ...